Preheat oven to 200°C. Pat the potato with a clean tea towel to remove excess moisture. Place on a large baking tray. Drizzle over 1 tablespoon of oil and toss to coat. Bake, turning occasionally, for 40 minutes or until golden and cooked through.

Step 2

Meanwhile, heat 1 tablespoon of the remaining oil in a large frying pan over medium-low heat. Cook the onion, stirring occasionally, for 20 minutes or until golden. Add the sugar and vinegar, and cook, stirring, for 5 minutes. Season with salt and pepper. Transfer to a bowl and cover with foil to keep warm.

Step 3

Heat the remaining oil in the pan over high heat. Cook half the steaks for 11/2 minutes each side. Transfer to a plate. Repeat with remaining steaks, reheating the pan between batches.

Step 4

Place 1 bread slice on each serving plate. Top with the lettuce, tomato, steak and onion. Top with remaining bread. Serve with the chips.

Vienna bread is only available when baked in-store at Woolworths.

Make it ahead: To save time, you can prepare some of this recipe ahead. Make the onion mixture (step 2) up to 3 days ahead. Store in an airtight container in the fridge and reheat before serving.